Creator Steve Franks and his writing crew are no strangers to bringing the kooky to the long-running USA Network series--who could forget the re-enactment of "Clue"?

Now, ahead of the launch of its eighth season (which rolls out next month), fans who have long anticipated hearing their favorite fake psychic detective (James Roday) and his best friend/pharmaceutical salesman (Dule Hill) belt out ditties, can now rest easy.

"Psych" will air a two-hour musical episode/movie this Sunday at 9 p.m.-- in which the cast plus guest stars including Ally Sheedy and Anthony Rapp will sing and dance their hearts out.

It's a labor of love for Franks, who moonlights as a musician (and who wrote the show's theme song). He wrote and directed the episode, plus penned the 14 songs with "Psych" music director Adam Cohen.

I am so calling it a movie because for as long as the show has run, I have always—we have a meeting at the end of the year, with the executives at Universal and they always say, "Hey, what are we doing for next year? What is your plan for next year?" and I always pitch a “Psych” movie. I was always hoping it’d be a feature film, but at the very least I thought if we stick around after a season is done and shoot two back-to-back episodes and make it a movie. So, this was sort of my way to do the “Psych” movie without having USA Network pay anything else extra for it.

I’m sure they were all for that. And it comes on the coattails of NBC’s “Sound of Music,” which got big numbers but was largely panned by critics and those active Twitter users. Are you happy about the timing, feel like people are in the mood for it?

It’s really funny because we shot this over a year ago. And [USA] liked it so much they called me and said they were going to make a special night out of it. I was so excited and then they said, "Yeah, we’re going to air it next year.” And I was like, “Whattt?” There's a big, huge plot point that this was supposed to betting up in the middle of Season 7, that now are built-in continuity errors—or, as I like to say, the basis for a really awesome drinking game. Although, technically, when you get to the very end, there is a way to sort of backwards explain how it could possibly be happening within this time frame in the show.

And it was something that had been brewing for a while in your mind, right?

It was one of those things. I wrote the theme song. When I sold the show, I had said, "Hey, I’m also doing the theme song.” And they were like, “Yeah, yeah, sure you are.” And we went in and we put it together and we recorded it. And they said, “Alright, this is fine. We’ll let him do it.” Fortunately, people seem to like the theme song, so from there it was like, “I want to do a whole musical.” This is from the pilot!

So we talked about it for so many years that we all collectively knew that it was going to be so difficult, but that it meant so much to us that we wanted to get it right, at least within our world. There’s so much effort and joy put into it at the same time because we’re all sort of fulfilling childhood memories, childhood bucket list with this project. Everybody really wanted it to be as great as it could possibly be. I hope we did it right. I know that I love it so much and am so happy with it. I can't stop listening. I can't stop singing the songs. I just got the mixed soundtrack that we’re going to release digitally the day-of…

Yes, “Psych” fans would riot if the songs weren’t made available.

I’ve had to, for the last six months, beat the drum of “are we going to release this?” I was like, “There needs to be a soundtrack. It needs to be this big thing.” I almost felt like I was pestering them to death to do it, but it’s so cool. It’s in my car now and I’m embarrassed because I can’t stop listening to it. It’s so weird because they were these songs that I wrote on acoustic guitar and brought in Adam Cohen, our composer, and months later we’re on the Eastwood Scoring Stage at Warner Bros. with a 50-piece orchestra and all I’ve kept thinking along the way is “this can’t possibly be happening.”

Let’s talk about the story. I assume there needs to be a rhyme or reason to the plot to make it work for a musical element, or can you just take a regular story idea and add some songs to it?

I watched a lot of these television musicals and many of them were, let’s say, less satisfying than I had hoped. Sometimes they never even bothered to explain why people were singing. At least with ours, there is a reason. It was always, ‘What was the device.’ There was actually a much more ambitious device that I started with that was a little bit—it wasn’t like mind-blowing, but it took a lot of explaining. So I sort of pared it down to make it easier to be digested. But it was always: I want to explain what’s going on. I don’t want to do cover songs—that was the No. 1 that I didn’t want to do. And I wanted to be sure that like any good film musical, any good Disney musical, any good Broadway show, the songs are about propelling a story forward in a big way and giving you the spirit and emotion of each scene.

I knew that the songs would be fun and funny just because of what our show is. So crafting the story, I thought, “this is the first time we’re going to do two hours.” So I needed it to not feel like it at the 50-minute mark to not have folks thinking, “oh, God, there’s another hour?” So the story itself is probably one of the most complicated and darkest mysteries we’ve done just because I needed to be able to prove people—because I’ve been saying, “Let’s do a ‘Psych’ movie for all these years—that this does stretch to two hours. I spent almost two months at the very beginning of the season—also running the show at the same time and developing the other four episodes that should have been shooting—and I spent every moment that I could building this story and making it more ambitious and consequently less ambitious one I realized we weren’t going to get any extra days or extra money, it was all just coming out of our budget. It was a tremendous and exciting creative endeavor to say, “OK, you’re going to get this much time, and it’s going to come within the regular run and we’re going to shoot 13 episodes before this and then we’re going to shoot the musical and then we’re going to shoot another musical after that.” I couldn’t run the tank down to zero with the cast.

And so you shot what is essentially two back-to-back episodes in the same amount of time it takes to film one episode. Are you insane?

Yes. I know. I know. It was the one thing that M-K Kennedy, who oversees production and basically writes our checks for us, asked us. When she finally found out that I was going to do the movie, she immediately took me to lunch. She sat down and said, “OK, how do you expect to pull this off?” And I thought so much about it because we talked so much about it and I realized that the only way we could do it was to make it the two-hour because then we could do this thing called cross-boarding, where the extra time we would get is because we’re not moving the trucks, we’re staying in the same location. For every location I used, I wrote it twice. You shoot all your police station scenes for two episodes in one day—you’re locked into one place each day and that gave us enough of a buffer with time and it saved us enough money to put on these elaborate numbers. There’s 14 songs in this thing, if you count the reprieves and the little asides, so it was one of those things that even cross-boarding and doing the two hours, every day was an adrenaline rush from the day I stepped out of the car.

And how about Dule and James—what was there whole initial reaction to rumblings about doing a musical?

I had done the exact same thing at the beginning of season 6. I said, “I’m closing my door and I’m writing this musical.” And then we got five episodes into the season and I just knew there was no way I was going to finish the musical. So when I said, “We’re doing the musical this year,” I think there was a certain degree of skepticism. And people had been like, “You don’t have to write it and direct it and do the songs, you know?” But that’s the fun of it! Why would I give that away to someone else? So it was a matter of me sufficiently carving out time, and luckily our writers were so good that I was able to escape the writers room for a while. Once they saw I was actually in my office and I pitched the entire episode to the writers with them all sitting around, with my acoustic guitar there singing the pieces of songs that I had—that was the moment they were like, “Oh, wow, you’re really going to do this.” I stopped being the boy who cried wolf.

I remember bringing James in. I had all the episode on my whiteboard in my office, and I pitched out the whole thing to him, and his face lit up. He was so excited. I thought, “If we fail, at least we’ll fail together with the same level of excitement.” He was in. And Dule has always been in. The dude tap dances on set. Kirsten Nelson called me up and said, “If you’re doing this, please put a song in there for me.” She was certainly the one who surprised me the most because she has such a tremendous range. I wish I had written more for her. And Tim Omundson, we always knew he had a good karaoke voice. And then we brought him into the studio and his rich baritone is filling up the room. He really stood out. Even Maggie [Lawson] was better than I expected her to be.

Musical episodes have been these weird sort of traditions of some sorts. Why do you think that is?

I don’t know. I guess because they’re fun to do. It’s a way to do something different without—gosh, I wish I knew the answer. Carlos Jacott said the best thing about our show once I showed him the script. After he saw the script, he said he realized that “Psych" has all along been a musical, just without the songs. So we naturally just transitioned into it. Our show just has that sort of kooky vibe.

And I wanted the episode to stand alone so that someday when someone turns it on, I don’t know where—maybe in a high school theater or maybe on Broadway—I want it to be fully contained. We set it up to be a full-on musical, not just a television musical. A few times that people have pulled it on to a tremendous effect and maybe that’s why people are open to it. They see what “Buffy” did with it. What “Scrubs” did with it.

Well, and people are already saying it stands alongside those. Does that make you feel compelled to do more? There are rumors the upcoming season might be its last.

I would absolutely would want to do another. I actually came from features and I wonder if anyone would buy an original musical straight to movie because it was so unbelievably terrifying, but life-changing at the same time. I would do it on this show in a heartbeat, I would do this as a feature version of this show as well because whenever they pull the plug on you, I think this show naturally transitions to not only being a feature film—maybe even six to eight features in the future.

When will you know the fate of the show?

We try to give a little bit of closure at the end of every season. We already shot all of season eight and there’s a little bit of closure there. I;m never going to kill off the entire cast because I love doing the show so much. We’ve always done the same number. It’s so strange. Our show just chugs along at the same pace. When that’s no longer good for USA and they say they want to move on to something else, we will gracefully bow out. The announcement could come at any time, or in between this year and next year. But we will have walked away with a smile on our face. We’ve gotten so much attention on this musical episode, it’s kind of a nice way to go out if we have to.

Is there a show out now, or even from the past, that you think would lend itself to a fun musical episode?

Sometimes it’s fun when you go the opposite direction—like a musical episode of “Breaking Bad.” That would probably be some drug-induced hallucination. But it’s done and there’s no way they can top what they’ve done! I don’t think they are going to reconvene to put a musical together.

I, personally, would have loved to see the “Magnum P.I.” musical. I think that would have been mind-blowing.

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